ACUS01 KWNS 172014
SWODY1
SPC AC 172013
Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0213 PM CST Tue Feb 17 2026
Valid 172000Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
CALIFORNIA AND PORTIONS OF NEBRASKA AND IOWA...
CORRECTED FOR NDFD COLOR FILL ISSUE
...SUMMARY...
Isolated strong thunderstorms will be possible across parts of the
West today through tonight. Isolated thunderstorms are also
anticipated across the Upper Midwest late this afternoon and
tonight.
...Eastern Nebraska and southwestern Iowa...
Near the base of a negative-tilt shortwave trough and a pronounced
100+ kt mid-level jet, strong ascent is expected to develop late
this afternoon amid a mixed and modestly moist air mass. Cool
mid-level temperatures and surface dewpoints in the 40s and 50s F
may allow a few hundred J/kg of buoyancy to develop. This
destabilization and strong ascent may support a fast-moving arc of
high-based showers/thunderstorms, particularly where surface
temperatures reach into the 60s and dewpoints hold above 40 F.
While buoyancy will be weak, dry low-levels and strong
dynamics/background flow could support efficient downward mixing of
momentum to the surface. Isolated severe/damaging gusts are possible
this afternoon and evening from parts of eastern NE into
west-central IA. Convection should weaken rapidly with eastward
extent
Elsewhere, isolated strong storms remain possible across portions of
the CA coast ahead of a strong secondary upper trough. This is most
likely overnight with a few damaging gusts or a brief tornado the
primary risks owing to very strong flow and modest inland moisture
advection. No changes were made to the outlook here, see the prior
discussion for more info.
..Lyons.. 02/17/2026
.PREV DISCUSSION... /ISSUED 1031 AM CST Tue Feb 17 2026/
...Synopsis...
Recent satellite imagery shows several disturbances across the
western CONUS, including a pair of low-amplitude shortwave troughs
within the belt of strong southwesterly flow extending from the
central Pacific into the central Plains and a deepening upper low
off the Pacific Northwest coast. Intense surface cyclogenesis is
anticipated ahead of the lead shortwave as it moves quickly
northeastward, with the resulting surface low forecast to move
across SD/NE, ending the period over southern MN. Evolution of this
surface low and parent shortwave, which will become increasingly
negatively tilted throughout the day and overnight, will result in
strong forcing for ascent from the Mid MO Valley into the Upper
Midwest this evening and overnight.
Farther west, the previously mentioned upper low is expected to drop
slowly southward as a strong jet (i.e. 100 kt at 500 mb) pivots
around its western and southern periphery. Very cold mid-level
temperatures and strong/persistent forcing for ascent will support
isolated thunderstorms along across much of the West coast
throughout the day and tonight.
...Coastal California...
Limited buoyancy is expected to develop along the near coastal areas
of CA as very cold mid-level temperatures (i.e. -25 to -30 deg C at
500 mb) associated with the upper low continue to advect into the
region. This buoyancy coupled with the strong forcing for ascent
could result in some deeper, more persistent updrafts across the
region today, both within the primary frontal band and any more
bowing line segments that may follow it. Given the robust deep layer
flow across the region, any deeper, more persistent updrafts could
result in some stronger, convectively augmented gusts. Additionally,
there appears to be enough low-level curvature to support a brief
tornado or two within the immediate coastal regions. Highest
potential for either hazards currently appears to be after 00Z in
the San Luis Obispo/Santa Barbara county areas.
...Upper Midwest...
Some low-level moisture return is anticipated across the region
ahead of the previously mentioned shortwave trough and associated
forcing for ascent. Even so, low-level moisture will still be
limited, with dewpoints likely remaining in the upper 40s to perhaps
low 50s. This is not expected to be enough moisture for surface
destabilization across most of the region, despite strong surface heating/boundary-layer mixing and steepening low-level lapse rates
in vicinity of the surface low/front. The only exception is across
far southeast SD and far northeast NE where a high-based storm or
two cannot be completely ruled out. Any that does develop could
produce an strong gust or two, although coverage will likely remain
less than 10%.
Across the Upper Midwest, capping may tend to largely prevail during
the day, with elevated thunderstorms becoming more probable
east-northeastward of IA into the MN/WI throughout the evening and
overnight. Instability does not appear strong enough to support
severe hail with this elevated activity.
$$
= = =
To unsubscribe from WX-STORM and you already have a login, go to
https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at
cnovy@cox.net and ask to be removed from WX-STORM.
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (1:2320/105)